COMMISSION 27 OF THE I. A. U.
           INFORMATION BULLETIN ON VARIABLE STARS
                     Number 2588

                                       Konkoly Observatory
                                       Budapest
                                       18 September 1984

                                       HU ISSN 0374 - 0676


        THE PHOTOMETRIC VARIABILITY OF EPSILON PERSEI

   Epsilon Persei (HR 1220, HD 24760, B0.7III (or B0.5V), V = 2.88)
has a long history of suspected light, radial velocity, and line profile
variations (reviewed by Smith 1984) going back to the beginning of this
century. Our own interest in this star arose from the photographic
spectroscopic studies of Bolton, Lane and Thomson at this Observatory;
they showed that this star exhibits striking line profile variations,
with as many as four components moving through the line profile on a
time scale of a few hours. More recently, Smith (1984), Penrod and
others have recorded the line profile variations of this star with
modern high-dispersion, high signal-to-noise spectroscopic detector
systems. They have found that it is possible to model these variations
with a combination of prograde sectorial non-radial pulsation modes.
Our previously-unpublished 1979 and 1980 photometric observations give
some indication of the nature of the photometric variability of this
star, and place some constraints on the pulsation modes which may be
present.
   Photometric observations were made by one of us (JRP) on five
nights in November 1979 and on seven nights in November 1980 using the
#4 0.4 m telescope at the Kitt Peak National Observatory in Arizona.
A 1P21 photomultiplier and pulse-counting electronics were used, along
with a three-magnitude neutral density filter to reduce the coincidence
counting effects. Measurements were made through a standard Stromgren
b filter, differentially with respect to the stars HR 1229 (A1, V = 6.2)
and HR 1234 (B9.5, V = 6.3). Magnitude differences were corrected for
differential extinction effects, and times s were reduced to the sun.
The magnitude differences, on the instrumental system, are shown in
Figure 1. A table of these data may be obtained from author JRP if
necessary. The standard deviation of the magnitude differences between
the comparison stars was 0.004m.


                               [FIGURE 1]

 Figure 1 - Photometric (b) observations of epsilon Persei relative to
            HR 1229. The constancy of HR 1229 was established relative
            to HR 1234. The error bars indicate the standard error of
            a single observation. The program star exhibits small but
            significant variability from hour to hour, but not from
            night to night or season to season.


   The main results of our photometric observations are as follows:
1. The scatter in the magnitude differences between epsilon Persei and HR 1229
  is considerably greater (sigma = 0.0074m) than that between HR 1229 and
  HR 1234 (sigma = 0.004m) whereas the reverse might be expected since the
  former two stars are brighter and closer together in the sky. This
  suggests that epsilon Persei is variable with a sigma of about 0.006m, which
  corresponds to a peak-to-peak amplitude of about 0.02m on the average.

2. The variations appear to take place on a time scale of hours. The
  variations from night to night, and between the 1979 and 1980 runs,
  do not exceed 0.01m in b.

3. Period analysis of the 1979 observations, using the methods of
  Scargle (1982) and Stellingwerf (1978), show a peak at a period of
  about 0.216 day. The statistical significance of this peak is 0.87
  (the probability that it is not due to chance), which is suggestive
  but not convincing. The power spectrum of the less numerous 1980
  observations also shows a peak at this period, but with an even
  lower significance.

4. Even after the removal of these peaks, there is a residual variance
  of about 0.01m. This suggests that two or more modes may be present
  (or that the variability may be irregular).
 
  It is not possible to draw any firm conclusions from our observations, 
because of their limited number, and because of the lack of
simultaneous spectroscopic observations. In November of this year, we
plan to obtain many more observations, and Myron A. Smith plans to
obtain simultaneous spectroscopic observations. We encourage other
observers to obtain careful photometric observations of this interesting
star.

   We thank Tom Bolton, Petr Harmanec, Don Penrod and Myron Smith
 for sharing unpublished data and for interesting and useful discussions.
 We also thank the Kitt Peak National Observatory for allocations of
 observing time, and the Natural Sciences and Engineering Research
 Council of Canada for an operating grant.


                       JOHN R. PERCY, MICHAEL BIETENHOLZ
                            and ALEX FULLERTON
  
                       David Dunlap Observatory,
                       University of Toronto,
                       Toronto, Canada M5S 1A1

References:

Scargle, J.D. 1982. Astrophys. J. 263, 835. [BIBCODE 1982ApJ...263..835S ]
Smith, M.A. 1984. Astrophys. J. in press. [BIBCODE 1985ApJ...288..266S ]
Stellingwerf, R.F. 1978. Astrophys. J. 224, 953. [BIBCODE 1978ApJ...224..953S ]